Digestive System

Nutrients

• Substances in food that provide raw materials and energy the body needs to live

• Our digestive system turns the chemical energy in these nutrients into energy we can use

Functions of the Digestive System

• Digests food into molecules the body can use (physical or chemical change)

• Absorbs nutrient molecules and carries them around the body (physical change)

• Eliminates waste material from unused nutrients

Digestion

• Process by which your body breaks down food into small nutrient molecules– Mechanical– Chemical

Mechanical Digestion

• Food is physically broken down into smaller pieces

• Begins in the mouth– Teeth– Movement of

smooth muscles

Chemical Digestion

• Chemicals produced by the body break foods into their smaller nutrients– Mouth– Stomach

Absorption

• Process by which nutrient molecules pass through the wall of your digestive system into your blood– The lining of the small intestine is covered

in villi that aid in absorption

Elimination

• Materials that are not absorbed leave the body as waste

• The waste material left over after food is digested must leave the body to prevent illness

Organs of the Digestive System

• Mouth Rectum• Esophagus Anus• Stomach Pancreas• Small intestine Gall

Bladder• Large intestine Liver

Mouth

• Digestion begins in the mouth– Mechanical – teeth– Chemical - saliva

Esophagus• Muscular tube that connects your

mouth to your stomach– moves food down into your stomach

using involuntary muscle

contractions (peristalsis)– Lined with mucus that

allows food to slide down

The Stomach

• J-shaped muscular pouch• Most mechanical digestion takes place

in the stomach• Chemical digestions also takes place

– Stomach secretes digestive juice (enzymes) that break down food

• Average adult stomach holds 2 liters• Mucus keeps the acids from burning a

hole in your stomach

Stomach

Modeling• Place the marble in the end of the tube

and squeeze it down into the balloon.

Modeling• What do you think this could be a model

of?

– What is the tube?– What is the balloon?– What is the marble?– What is the soap?

esophagusstomachfood

saliva and mucus

Small Intestine• Where most of the chemical digestion

takes place • Where most of the absorption takes

place• Covered in villi which

enlarge the surface area

Small Intestine

Liver• Breaks down medicines and other

chemicals• Produces bile that breaks up fat

particles• The gall bladder

stores bile

Pancreas• Produces enzymes that flow into the

small intestine• Secretes insulin• Causes diabetes when it does not make

insulin

Large Intestine

• Last section of the digestive tract• Where water is absorbed• Vitamin K is made by bacteria in the

large intestine

Rectum and Anus

• Rectum – end of the large intestine, forms the solid waste– elimination

• Anus – muscular opening at the end of the rectum– elimination

Which cell parts are like the digestive system?

Which one makes energy?

Which one helps get rid of waste?

mitochondria

lysosomes

Which one allows materials to pass in and out?

cell membrane

The digestive System Interacts with:

The digestive system depends on the muscular system to move the food through and for mechanical digestion, the circulatory system to move the absorbed nutrients around the body and the respiratory system to supply it with oxygen